Alternating-current relay



Oct. 9 1923.

W. D. HAILES ALTERNATING CURRENT RELAY Filed 000- 2l. 1921 '4Sheets-Sheet l INVENTOR m4 @./MJ

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w. D. HALE-s ALTERNAT'ING CURRENT RELAY Filed Oct. 2l, 1921 4Sheets-Sheet 4 NNW" fri JM@ 1 INVENTOR ACQ ATTORNEY Patented Oct. 9,1923.

UNITED STATES PATENT OFFICE.

WILLIAM D. HAILES, 0F ALBANY, NEW YORK, ASSIGNOR TO FEDERAL SIGNAL COK-PANY, 0F ALBANY, NEW YORK, A CORPORATION 0F NEW YORK.

ALTERNATING-CUBRENT RELAY.

Application filed October 21.192L Serial No. 509,284.

To all whom it may concern.'

Be it known that I, IVILLIAM D. HAILES, a citizen of the United States,residing in the city of Albany, county of Albany, and State of New York,have invented certain new and useful Improvements in Alternating-CurrentRelays, of which the following is a specification.

My invention relates to alternating current relays of the type whereincurrents in two co-operating wmdings or sets of windings are required toshift the movable member to an operated position.

One object of m invention is the provision of arelayy o this type inwhich all tendency of the movable member to creepr or drift iseliminated, thereby avoiding any possibility of this member falselyassuming or remaining in an operated position.V

Another object of my invention is the provision of a relay which is soconstructed that when onl one winding or set of windings is excite anelectro-magnetic force isl exerted on the movable member tending to moveit to the neutral position, this force 'being in addition to the usualmechanical counterweighting force exerted on this member. Thiselectrical counterweighting force is present and effective underabnormal-as well as normal conditions of voltage, frequency and phaserelation of the current in the excited winding, and under abnormal aswell as normal conditions of the circuit for the unexcited winding.

I will describe one form of relay embodying my invention, and will thenpoint out the novel features thereof in claims.

In the accompanying drawings, 1 is a view showing in elevation one formDf relay embodying my invention. Fig. 2 is a vertical sectional viewtaken on the line II-II of Fig. 1 and looking in the direction indicatedby the arrows. Fig. 3 is a top plan view showing the electro-magneticportions of the relay shown 1n Figs. 1 and 2, the other parts beingomitted and the windings being illustrated so1newhat-d1agrammatically.Fig. 4 is a vertical sec-tional view on the line IV-IV of Fig. 3 lookingin the direction indicated by the arrows and showing the movable memberor rotor in its neutral o r biased position. Fig. 5 is a view similar toFig. 4 but showing the rotor one-third of theway towards one operatedposition. Fig. 6 is a view similar to Figs. 4 and 5 but showing therotor two-thirds of the wa towards the said full operated position. 4ig.7 is a. view similar to Figs. 4, 5 and 6, but showing the rotor in thesaid full operated position and indicatin in dotted lines the other fulloperated position of the rotor.

Similar reference characters refer to` similar parts in each of theseveral views.

Referring first to Figs. 1, 2 and 3, the operating parts of the relayare enclosed by a bottom plate 10, side walls 11 and atop plate 12.

Attached to the bottom plate 10 is a. base member 13 provided with twoupsta'nding.

end plates 13, 13l which vin turn support a metallic frame 14..v Thisframe carries the magnetizable cores of the relay, as well as the rotorand the other movable parts immediately attached thereto. i

The relay is provided with two magnetizable cores, viz., an exciter coreA and a. stator core B, each of which, in conformity with usualpractice, is made up of a large number of laminations of magnetizablematcrial such as soft iron. The exciter core A is attached by screws 15to the upstanding arms 14"* on frame 14 as best shown in Fig. 2, whilethe stator core B is similarly attached to the under side of this lframeby screw 16. The shapes of the cores are best shown in Fig. 3. Theexciter core A is in the form 'of a hollow rectangle provided with amiddle connecting leg 17, which leg carries an. exciting winding 18.This core has no air gap either inthe rectangular portion or theconnecting leg. The stator core B also comprises a hollow rectanglehaving a central pole-piece 19 provided with an air gap 19, and twomotor polepieces 20 and 21 provided respectivelyl with air gaps 20l and21. Each motor polepiece of this core carries a coil 22, which coils ashere shown are connected in series and together constitute the statorwinding oi the relay. The movable member of the relay includes arotordesignated R, of nonmag'netizable, electro-conductive material such ascopper or aluminum, of such shape as tolform a closed circuit in whichcurrent flows, as distinguished from forming a series of circuits forlocal eddy currents.

It is preferably in a single sheet and of a shape similar to that shownin Figs. 4, 5, 6 and 7, from which it will be clear that it comprises(see Fig. 4) two limbs 23a and 23b connected at their upper ends by amember 24 and at their lower ends by two arms 25a and 25". The rotor Ris carried by arotor support 26 having a central vertical forked arm 26ato which the upper or. arcshaped portion of the rotor is attached byscrews 27. This rotor support also comprises two vertical end arms 26band 26C carrying endV plates 281 and 23C which, together with the endarms, constitute suitable mountings for two pivot pins 29b and 29'. Thetwo pivot pins are journalled to turn in recessed bearing screws 3()band 30 respectively which are mounted in upstanding end plates of theframe 14 as is clearly illustrated in Fig. 2, so that it will be evidentthat the movable member comprising the rotor R and support 2G is free tooscillate as a unit in the frame 14. The rotor is so located that itpasses freely through the air gaps 19a, 2O1 and 21 in the stator core B.The rotor R is biased, as will hereinafter appear, to the position shownin Figs. 1 and 4, and its mcvements in opposite directions from thisposition are limited by suitable energy-absorbing stops 43 and 48a solocated as to be engaged by the rotor arms 25 and 25b respectively.

The end plate 281 on rotor support 26 constitutes an operating eccentricas best shown in Fig. 1, and this eccentric co-acts with two rollers 31and 31 pivotally mounted in an operating fork 33 and in pivot brackets32 which are attached to this fork. The operatimg'v fork extendsupwardly and is rigidly attached to a contact finger support 34 byscrews 36, which support yis mounted to oscillate on a rod 35 carried bybrackets 37 and 37 attached to the top plate 12. The upper end of theoperating fork is in the form of a yoke 39 which straddles the rod 35.

The contact finger support 34 carries four sets of contact fingers (l.D, E and F, each set comprising a plurality of parallel fingers arrangedside by side as viewed in Fig. 2 and directly behind each other asviewed in Fig. l. For convenience T will term fingers D the normalfingers. fingers C the reverse fingers. and fingers E and F the backcontact fingers. The cont-act fingers C are attached to arms 47 which inturn are mounted on studs 40 of insulating material supported on theunderside of the finger support 34. Each contact finger D is similarlyattached to an arm 47l mounted on studs 41` while each contact finger Eand F is attached to an arm 47b which is mounted on insulating studs 42located on the upper surface of the finger su port 34. Each contactfinger C co-acts witfi a fixed contact member C fixed in the top plate12 while each contact finger D co-acts with a similar fixed contactmember Da also supported in the top plate 12. Similarly the contactfingers E and F cooperate with fixed contact members E and Ferespectively which project downwardly from the top plate 12.

The finger support 34 is biased to the neutral or intermediate position,in which it is shown in Fig. 1, by counter-weights 43 and 44 each comrising a threaded rod carrying an adjusta le weight 49. Thesecounterweight rods are pivotally attached tr: the contact support 34 atpoints 43a and 44 respectively, and their downward movements withrespect to the support are limited by studs 45 and 45 carried by thesupport. The free ends of the counterweight rods 43 and 4-4 are providedwith pins which co-act with slotted arms 46 and 46a supported by anddepending rfrom the top plate 12.

The operation of the contacts by the movable member is as follows: Thenormal or neutral position of the movabl'e member is the position inwhich it is shown in Fig. l. the member being primarily biased to thislposition due to the fact that the center of gravity of the rotor R isbelow the line of the pivot screws 30b and 30C. iVhen the movable memberoccupies this position. the ContactI support 34 occupies theintermediate or neutral position wherein it is shown in Fig. 1, beingheld in this position by the action of eccentric 28b on the rotors 31and 31'* as well as by the biasing forces exerted by the counterweights43 and 44. iVith the contact support in this position contacts C-CR andD-Da are open while contacts E-F.a1 and F-Fa are closed. l will nowassume that rotor R is swung to the right, that is, in counterclockwisedirection as viewed in Fig. l. This causes countercloclnvise rotation ofthe eccentric 23b which in turn causes counterclockwise movement of theopw erating fork 33 and the contactfinger support 34 around the rod 35.This movement of' the finger `support 34 causes contacts D-Da to Vcloseand contacts E-E to open` the other contacts remaining in the conditionsin which they are shown in Fig. 1. This movement of the contact support34 also elevates the right hand counterweight 44, such movement of thecounterweight being unopposed owing to the slot in the restricting arm46". Counterweight 43 performs no function at this time owing to thefact that its free end is supported by the left hand restricting arm 46.

iVhen the torque'tending to swing the rotor R in counterclockwisedirection is removed, this rotor together with the rotor support 26returns to the intermediate or neutral position owing to the biasingforces lll) acting on the rotor, and the finger support 34 also returnsto its neutral position owing to the action of the eccentric 28b and theaction of the counterweight 44.

lVhen a torque is exerted on the rotor R in the opposite direction sothat this rotor swings in clockwise direction as viewed in Fig. 1, itwill be obvious that the finger support 34 is likewise turned inclockwise direction thereby elevating counterweight 43; the result ofthis movement is that contacts C-C are closed while contacts F--Fabecome open. When the torque on rotor R is removed, the movable memberand the finger support 34 return to their intermediate or neutralpositions, so-that lthe parts of the relay are restored tothe positionsin which the are shown in Fig. 1.

ferring now to Fi s. 3, 4, 5, 6 and '7 the operation 0f the rotor by the'electro-magnetic members of the relay is as follows. As long asalternating current is supplied to exciter Winding 18, an alternatingcurrent flow is induced in the rotor R due to translformer action, itbeing noted that this rotor constitutes a closed secondary of atransformer of which the primary is the exciter winding 18 and themagnetic core is the exciter core A. There being no air gap in theexciter core, it is obvious that this transformer action is highlyefficient so that a comparatively small amount of current in the winding18 will induce a comparatively heavy current in the rotor R. I will nowassume that while the exciter Winding is supplied with alternatincurrent, another alternating current of te same frequency and preferablyin phase with the exciter current is supplied to the stator winding 22.The magnetic flux passing through the motor pole pieces of the statorcore will cooperate withthe magnetic fiux due to the current in therotor R to swing this rotor in one direction or the other depending onthe relative instantaneous polarities of the currents in the twowindings. Assuming that this relative instantaneous polarity is such' asto swing the rotor in counterclockwise direc-k tion, the rotor will moveto the position in which it is shown in Fig. 7 in which position itsmovement will be arrested by the stop 48n shown in Fig. 1. If thecurrents in the two relay windings arel of opposite relativeinstantaneous polarity, the rotor R will be swung to the positionindicated by the dash lines in Fig. 7, in which position itsI movementwill be arrested by the stop 48 of Fig. 1. When the 'rotor swings in thefirst mentioned direction it will of course close contactsD-D of Fig. 1,while when it swings in-f-the second mentioned direction itwill closecontacts C-C of Fig. 1.

As already pointed out, the, operating parts of the relay are biased bythe neutral or' intermediate position.

.posing thermore. when the rotor R is not in the neutral position andeither the stator winding alone or the exciter winding alone isreceiving alternating current, an electro-magnetic force is exerted onthe rotor tending to return it to the neutral position, regardless ofwhether the de-energized winding is on open circuit or short circuit.The reasons for this electro-magnetic bias are as follows:

I will first assume that the rotor R is' in the operated position shownin fulLlines in Fig. 7, and that the exciting winding 18 becomes(le-energized and is on open circuit,

While the stator winding Q2 continues to be energized. Under thiscondition there is an electro-magnetic force acting on the arm 25h ofthe rotor R which arm is standing in the air gap of the motor pole pieceQ1, and which force is the well known blowout force which accompanies anatte-nipt to enter a sheet of electro-conductive material between a pairof pole pieces carrying alternating magnetic flux. It will he noted fromFig. 7 that the arm 25 fulfills the conditions of such a sheet enteringa magnetic field for when this arm is in the position shown, its centerof gravity has not yet passed the geometrical center ot' the pole pieces21 and the arm is therefore still entering the magnetic field. This armwill consequently, unless opposed, move out of the magnetic Iield in thedirection from which it entered. Since this blow-out Ytorce is in thedirection of the gravity bias of the rotor, the rotor will be urged bythe electromagnetic i'orce to return towards its neutral position. Onapproaching the neutral position (see Figs. 6, 5 and 4 in the ordernamed) it will be observed that the blowout force acting on the arm 25constantly decreases in intensity, while a similar opsmallelectro-magnetic blow-out` force will be exerted on the arm 25 as thelatter arm approaches the motor pole pieces 20. This opposingblow-out'force together with the gravity bias will bring the rotor torest in its neutral position because the whole structure of the relay issymmetrical about a vertical axis through the rotor when in the neutralposition, and so in this position the two arms 25 and 25b areequidistant from the geometrical centers of the motor pole pieces 20 and21. In this neutral position therefore the mechanical bias is satistiedand the two blow-out forces are equal and opposite.

The electro-ma etic biasing force which I have just described is presentfor exactly the same reasons if the exciting winding 18 is placed onshort circuit after being deenergized. Furthermore this electro-magneticbiasing force will be increased by an increase in the field strength ofthe motor that an abnormal voltage is applied to 'the stator winding 22;the reason for this, of course, is that the blow-out action of the motorpole pieces will be increased by an increase in the intensity of themagnetic flux in the pole pieces. Again, this biasing action will occurshould the stator winding 22 receive alternating current or pulsatingcurrent of a frequency other than-the current fdr which the relay isdesigned. This is obvious because the blow-out action is presentregardless of the character of the current supplied, to the statorwinding, provided only that this current be of varying intensity.

I will now consider the condition in which the stator winding'22 becomesde-energized while the i'otor is in the position shown in full lines inFig. 7, and while the supply of alternating current to the exciter wining 18 continues. there is an electro-magnetic force acting on the rotorand tending to urge it to include a magnetic path whose reluctance is-the minimum of all the paths which vit is free to select.- Inthepresent structure t-he impedance of the exciting winding 18 varieswith changes in the impedance of the rotor R for the same reason thatthe primary of any transformer varies with variations of the impedanceof the secondary. For a given total flux to be carried through theaperture in the rotor the reluctance of the magnet-ic path through therotor will be lowered when the cross-section available to carry suchflux is increased. It follows that the impedance of this rotor will bemaximum when the maximum area of the central pole piece 19 is -presentedto the aperture in the rotor. Since this condition exists when the rotoroccupies its neutral position, it follows that the impedance of therotor and.v therefore of the exciting winding will be maximum when therotor occupies the neutral position, and so the rotor will be driven tothis position by the electro-magnetic forces under the c'onditions whichI have stated.

The electro-magnetic biasing action under the conditions last assumedwill also exist for the same reasons and to the same extent if thestator winding or any part of it is placed on short circuit after`becoming deenergized. The biasing force will also exist in the case ofabnormalvoltage on the exciting winding.

It will be noted that to move the rotor from the neutral position to anoperated position there must be present simultaneously a suitablecurrent in the rotor and a suitable magnetic eld with which the .rotorcurrent can co-act. Inasmuch as current can be supplied to the rotor byinduction only, it follows that the relay is inoperative on directcurrent.

Furthermore it is apparent that the relay In. the relay illustrated inUnder4 these conditions rotation of the can operate only when thecurrent in the rotor and the magnetic flux in the motor poles of thestator are in synchronism, and so it follows that the rela will notoperate if currents of two diffgrent frequencies are supplied to the twowindings.

Considering now the torque characteristics measured at the rotor shaft,it is to be noted that the torque available to do work is not constantthroughout the travel of the rotor from the biased position to anoperated position, and that the orque curve can be varied to suit aparticular requirement.

the present application it will be noted that while one arm of the rotoris at all times within the tiled of, or actually in the air gap of, oneof the motor pole pieces, the maximum area of rotor material ispresented to motor pole piece flux when the rotor is in the operatedposition, and consequently the torque on the rotor is maximum at thistime. Inasmuch as this condition ,is gradually approached, as the rotorapproaches the full operated position, it is obvious that the torquecurve rises as the rotor approaches its operated position so that as thecontact load of the relay increases the torque exerted on the rotor alsoincreases, thus enabling the rotor to satisfactorily meet the loadimposed upon it at the contacts.

I have found byexperiment that by changing the relation between themotor pole pieces of the stator and the shape and disposition of thelimbs and arms of the rotor, various forms of torque characteristics maybe obtained. This will be apparent when it is noted that`the rotortorque is proportional to the product of the component of the rotorcurrent in time phase with the stator field flux, the stator field flux,some geometrical function of the. angle which the direction of rotormakes with the radius of point of the rotor consideredand its distancefrom the center of rotation.

To sum up the foregoing, a relay embodying my invention is characterizedby the fact that when either winding alone is supplied with alternatingcurrent an electromagnetic force is exerted onthe rotor tend- -ing tobring the latter to its neutralv position, this being true whether thede-energized winding is on short circuit or o en circuit, and thiselectro-magnetic biasing force is augmented by an over voltage in eitherof the windings.

One important lfeature of the relay is that the energy supplied to thestator winding can be increased to the limit imposed bv the heatradiating capacity of the windings without interfering with quickmovement of the rotor from an operated position to the neutral position.

Another important characteristic is that the torque available to do workincreases as the rotor approaches the operated position. Anotherimportant characteristic is that the relay is inoperative on directcurrent.

Relays embodying my invention are particularly well adapted for use inrailway signaling systems. When so used the stator winding 22 may beconstantly supplied with alternating current from a suitable source suchas a transmission line. while the exciting winding 18 may be suppliedwith current from a track circuit, the track circuit being in turnsupplied from the same transmission line through a pole changer. It willbe apparent, therefore, that when the track circuit is unoccupied therotor will swing to one operated position or the other depending uponthe position o the pole changer, and will assume its neutral orintermediate position when the track circuit becomes occupied by a caror train, in which event the supply of current to the exciting windingis of course discontinued or reduced to a comparatively low value. i

By providing the relay with coil 18 adapted to be connected to linecircuit as distinguished from track circuit, this device may be`controlled from line circuits with pole changers as a -position linerelay, the rotor R taking a position to the right or the left inaccordance with the relative polarity of the current in the excitingwinding 18 and stator winding 22 or assuming an intermediate positionwhen either the stator winding 22 or the exciter winding 18 or both maybe de-energized.

The foregoing disclosure covers the operation of the device through.9i-positions of operation, one on eitherrside of the de-energizedbiased position. It will be obvious that in the event that 3-positioncontrol of the rotor R is not required, the device mightbe biased toassume its intermediate position as shown in Fig. 4 against a fixed stopwhich would prevent the rotor from moving toward the dotted position ofFig. 7 With this construction, the rotor would have an operated positioncorresponding to Fig. 6 and a de-energized position corresponding toFig. 4. This construction would impose the condition that the rotorwould not assume an operated position unless'the winding 18 wasenergized with currents of predetermined polarity, with relation to thecurrents in windin 22; currents in winding 18 of the opposite polaritymerely tending to hold the rotor R against the fixed stop in addition tothe counterweight. With this construction, the device is adapted for 2-position .operation on track or line control as distinguished from the-position control as mentioned above.

Although I have herein shown and described only one form of relayembodying my invention, it is understood that various changes fandmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. An alternating current relay comprising an apertured disk-like rotorof electroconductive material. means for inducing an alternating currentin said rotor, means for creating an alternating magnetic 'flux forco-operat-ion with said current to move the rotor, and a contactcontrolled by said rotor.

2. An alternating current relay comprising a rotor constituting a closedcircuit of electro-conductive material, means for inducing analternating current in said rotor, other and independent means forcreating an alternating magnetic fiux for co-operation with said currentto move the rotor, and a contact controlled by said rotor.

3. An alternating current relay comprising a rotor constituting a closedcircuit of electro-conductive material, a magnetizable core passingthrough said rotor and provided with a windin whereby alternatingcurrent in said winding will induce alternating current in said rotor,other and independent means for creating an alternating magnetic flux toco-operate with the current in said rotor to move the rotor, and a`contact controlled by said rotor.

4. An alternating current rela comprising a rotor constituting a closeelectrical circuit, an exciting winding in inductive relation to saidrotor for creating alternating current in the rotor, other andindependent means for creating an alternating magnetic flux tcco-operate with the current 1n said rotor to move the rotor, and acontact controlled by said rotor.

5. An alternating current relay comprising a rotor constituting a closedelectrical circuit, an exciting winding in inductive relation to saidrotor for inducing alternating current in therotor, thereby producing analternating magnetic flux at right angles to the plane of the rotor,other and independent means for creating a second alternating magneticflux to co-operate with said rotor iiux to move the rotor, and a contactcontrolled by said rotor.

6. An alternating current relay comprising a rotor constituting a closedelectric circuit, a closed magnetizable core passing through said rotor,a Winding on said core whereby alternating current in said Winding willinducejalternating current in lsaid rotor, other and independent meansfor creating an alternating magnetic flux to c0- operate with thecurrent in said rotor to move the rotor, and a contact controlled bysaid rotor. f

7. An alternating current relay comprising a stator core having threeparallel pairs of confronting pole-pieces' magnetically connected attheir outer ends, a stator winding for said core, a closed electricalconductor mounted to move between said pole-pieces and biased yto suchposition that it is symmetrically disposed with respect to thepolepieces, means for inducing alternating current in said conductor,and a contact controlled by said conductor.

8. An alternating current relay comprising a stator core having threeparallel pairs of confronting pole-pieces magnetically connected attheir outer ends, a stator winding for said core, a closed electricalconductor mounted to move between said pole-pieces and biased to suchposition that the middle pole-piece substantially registers with theopening in said conductor and two opposite limbs of the conductor liebetween the middle pole-piece and the two outer pole` piecesrespectively, means for inducing alternating current in said conductor,and a contact controlled by said conductor.

9. An alternating current relay comprising a rotor in the form of aclosed ring of electro-conductive material biased to an intermediateposition and movable in opposite direction therefrom, means for inducingalternating current in said rotor, a stator core having three parallelpole-pieces each perpendicular to the plane of the rotor and eachprovided with' an air gap to accom-` modate the rotor, said pole-piecesbeing so disposed that when the rotor is in its intermediate positionthe middle pole-piece substantially registers with the opening in therotor and two opposite limbs of the rotor register substantially withthe spaces between the middle pole-pieces and the two outsidepole-pieces respectively, an energizing winding for said stator, and acontact controlled by said rotor.

10. An alternating current relay compris` ing a ring-like rotor ofelectro-conductive material formed by two electrically connect! eddiverging limbs and two electrically connected diverging arms all insubstantially the same plane and the free ends of the arms beingelectrically connected respectively with the free ends of the two limbs,said rotor having a neutral position and movable in opposite directionstherefrom to two operated positions, a stator core having three parallelpairs of confronting polepieces between which said stator is free tomove each pair being perpendicular to the plane of the rotor, therelations of the parts being such that when the rotor occupies theneutral ister substantially with the spaces between the arms and limbsof the rotor whereas the two rotor limbs lie between the middlepole-piece and the two outer pole-pieces respectively, and that when therotor is in either operated position one arm registers position themiddle pole-pieces regwith one outer pole-piece or the other armregisters with the other outer pole-piece, a winding for said statorcore, and contacts controlled by said rotor.

11. A relay rotor comprising two electrically connected diverging limbsand two electrically connected diverging arms all in substantially thesame plane, the free ends of the two arms being electrically connectedrespectively with the free ends of the two limbs.

12. A relay comprising a movable member mounted to oscillate, aneccentric fixed to said member, a contact supportmounted to oscillate,and an operating arm fixed to said support and provided with twofollowers cooperating with said eccentric.

13. A relay comprising a stator having two pole-pieces each providedwith an air gap, a winding for said stator, a rotor mounted to move'insaid air gaps, and means including a core passing through the rotor forcausing alternating current to flow in said rotor.

14. A relay comprising a stator having two pairs of confronting poles; amember carrying a conductor which is normally midway between said pairsof poles but which is movable away from the field of one pair of polesand into the field of the other pair, and means including a core passingthrough the conductor for creating alternatmg current in said conductor.

15. A relay comprising means for creating an alternating magnetic field,an electrical conductor mounted to move in said field, means forcreating an alternating current in said conductor comprising a corepassing through the conductor, and a contact controlled by saidconductor.

16. A relay comprising means for creating an alternating magnetic field,an electrical conductor mounted to move in said field, a closed magneticcore passing through said conductor, a winding on said core andtherefore in inductive relation to said conductor, and a contactcontrolled by said conductor.

17. A relay comprising a movable member in the' form of a closedconductor biased to one position, and electromagnetic means includingtwo windings for exerting a force on said member in opposition to thebiasing force when both windings are supplied with alternating currentsof the same hase and for exerting a force on said mem er in thedirection of said biasing force when either ot said windings is suppliedwith alternating current and the other is not.

18. A relay comprising a movable member in the form of a closedconductor biased to one position, and electromagnetic means includingtwo magnetic circuits and a winding for each circuit for exerting aforce on said member in opposition to the biasing force when bothwindings are supplied with alternating currents of, the same phase andfor exerting a force on said member in the direction of said biasingforce when either of said windings is supplied with alternating cur rentand the other is not.

19. A relay comprising a magnetic core y having two parallel legs eachprovided with whereby when said conductor and said winding are bothenergized the conductor will be moved toward its second position byinductive reaction, when the conductor is de-energized and the windingis energized the conductor will be urged toward its normal position dueto reaction between the said conductor limb and the second leg, and whent the conductor is energized and the winding is de-energized theconductor will be 'urged towards its normal position because in suchposition the reluctance of the magnetic path through the conductor isminimum.

20. A relay comprising a magnetic core having two parallel legs eachprovided with and'air gap, a winding for said core, a movable memberhaving a closed ring-like conductor biased to a normal position whereinit substantially encircles one leg and movable in said air gaps to aposition wherein one limb of the conductor approaches the geometricalcenter of the other leg, and means for creating current in saidconductor; whereby when said conductor and said Kwinding are bothenergized the conductor will be moved toward its second position byinductive reaction and when either the conductor or the winding isenergized and the other is not the conductor will be urged to its biasedposition and positively held there by electromagnetic action.

` WILLIAM D. HAILES. Witnesses:

WADE H. REICHARD, EUGENE SEITz.

